AMNIO ANTIBODIES

I WAS WONDERING IF ANYONE KNOWS ANYTHING ABOUT THIS SUJECT. I KNOW IT HAS SOMETHING TO DO WITH THE FATHER'S BLOOD MIXING WITH THE MOTHER'S AND CHANGING YOUR ANTIBODIES OR DNA. IT ALSO IS MORE COMMON IN MULTIPUL BIRTHS. IF ANYONE KNOWS MORE AND CAN EXPLAIN IT IN BETTER TERMS I WOULD APPRICIATE IT BECAUSE MY FRIEND IS GOING THROUGH THIS AND I WANT TO BETTER UNDERSTAND IT. THANK YOU